Nickel plating



Patented Aug; 17, 1943 NICKEL PLATING Rudolf Lind, Euclid, William J. Harshaw, Shaker Heights, and

Ohio, assignors Kenneth E. Long, South Euclid, to The Harshaw Chemical Company, Elyria, Ohio, a corporation of Ohio No Drawing.

Original application March 11,

1940, Serial No. 323,380. Divided and this application March 31, 1941, Serial No. 386,030

9 Claims.

This invention relates as indicated to electrodeposition of metals and more specifically, to a process of and materials for use in the process of electrodepositing nickel characterized in that the resultant nickel plate, as deposited, is both bright and ductile. More particularly, the present invention has to do with new addition agents for producing the above-named desirable characteristics in the nickel plate and which may be used with acid nickel baths of usual composition operating under usual conditions.

In order to properly evaluate invention, it is necessary to define brightness and ductility or brittleness, terms used in the old art, but used loosely to describe all degrees of brightness or brittleness.

BRIGHTNESS It is obvious that an extremely thin deposit of nickel over a highly buffed surface will appear bright. Bright plates of this type have been made for years and are well recognized in the art. Their limitations are that if the plated article is exposed to the atmosphere or to wear, the plate soon disappears or wears off. A plate thin enough so that it will retain substantially the full brightness of the polished base metal is impractical for use even as a base for the electrodeposition thereover of a protective coating of other metals such as chromium. If a heavier deposit is plated out, the-brightness of the highly buffed surface diminishes and a gray or white dull deposit is obtained.

A nickel plate which is thick enough to be practical for use and which is bright without buffing is not only desirable per se, but it is particularly advantageous where it is destined for use as the base for an electrolytically deposited chromium plate, since, if the nickel plate does not require to be polished and buffed, a relatively thin plate gives the same protection as the necessarily heavier gray plate, some of which must be taken off in the polishing to secure the desired brightness. Furthermore, a very considerable saving in time and in cost on the production of plated articles becomes possible, whether with nickel plate per se or with additional chromium finish.

Various so-called addition agents have been proposed from time to time for inclusion in nickel plating baths in order to control or affect the.

character of the electrolytically deposited metal.

' One principal objective in such modification of the present the plating bath has been to increase the brightness or luster of the deposited metal.

Many of these previous nickel plating addition agents have allowed a much heavier deposit of nickel to be built up before the brightness of the base metal was materially diminished. When polished articles are plated in such baths, the deposit is not truly bright but merely, at best, has the same character as the base metal. The brightness produced by such addition agents may, therefore, be characterized as brightness diminishing with increased thickness of plate on a polished surface.

Others of these previous nickel plating addition agents have produced a plate which would maintain the brightness of the polished base surface, even though the plate was built up to a substantial thickness. They would not build up any substantial brightness on an unpolished surface and, at best, would'only very slowly build up brightness on an unpolished surface when plates of extreme thickness were made. The brightness produced by such addition agents may, therefore, be characterized as brightness maintaining itself with increased thickness of plate on a p01- ished surface,

The addition agents of the present invention produce a plate that not only maintains the brightness of the most highly polished base metal, irrespective of the thickness of the plate within practical limits, but also increases in brightness with increase in thickness of the plate on an unpolished surface. The brightness produced by such addition agents may, therefore, be characterized asfbrightness increasing with thickness of plate on an unpolished surface.

DUC'I'ILITY The question of ductility is one of vital concern to the plater. In general, all bright plates are harder and, therefore, more brittle than ordinary dull nickel. vWhen enough of many of the peviously employed addition agents was added to a bath to produce a bright plate, the plate was often too brittle for commercial use and yet if less addition agent was used, the plate would not be fully bright.

A test for ductility may be made by plating on a non-adherent surface and stripping off the foil and handing it double on itself. thick which will pass this test without breaking is considered to have good ductility. A plate .0005" thick which will just pass this test is considered to have passable ductility. A plate .0002" thick which will not pass this test without breaking is considered to have poor ductility.

The addition agents of the present invention not only produce plates with the highest order of brightness, but also with a high order of ductility as defined by the above scale. This is desirable and essential to the practical use of bright nickel plating.

The principal object of the present invention, therefore, broadly -stated, is to provide an improved process of and materials for use in the process of electrodepositing nickel which will not only render the nickel plate desirably bright but which will also preserve or render the plate desirably ductile.

Other objects of our invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter more particularly pointed out in the claims, the following description setting forth in detail certain approved modes of operation of our process and combination of ingredients embodying our invention, such disclosure constituting, however, but certain of various forms in which the principles of our invention may be used.

Broadly stated, our invention comprises the discovery that by the use in acid nickel electrolytes of a plurality of addition agents respectively selected from certain different classes of compounds, we are able to produce deposits which are superior to those obtainable by the use of addition agents from either one of such classes alone. We find that the addition agents from one of said classes, although characterized by an embrittling tendency, are productive of extreme brightness when used in combination with addition agents from the other class and that addition agents from said other class not only cooperate in the production of brightness but also exert a ductilizing effect in the combination. The use of one addition agent from each class is preferable but a plurality from each class can be used successfully. Our

A plate .001"

cooperating addition agents are suitable for use in a wide variety of nickel electroplating solutions. We have found them to be very effective in aqueous acid nickel sulfate solut ons and aqueous acid nickel chloride solutions. Among the nickel sulfate solutions in which they are effective ar aqueous acid solutions of nickel sulfate, nickel sulfate and nickel chloride, nickel sulfate and sodium chloride, nickel sulfate and hydrochloric acid, nickel sulfate and ammonium chloride, nickel sulfate and alkali metal chlorides other than sodium chloride, the chlorides serving to produce.

good anode corrosion. Our addition agents are effective in nickel chloride solutions with and without nickel sulfate. In each of said solutions it is desirable, although not necessary, to employ boric acid or another suitable buffering agent.

We prefer to employ a bath containing nickel sulfate together with a suitabl chloride, preferably nickel chloride and a suitable buffer, preferably boric acid. We prefer to employ one or more addition agents from one of said classes in quantity to produce the desired brightness and one or more from the other class in quantity to overcome'to a. substantial extent the resulting embrittling tendency.

Representative of separate classes of compounds I which, when used in combination as above stated, produce improved results, are those classes of compounds which may be identified as (1) safranine compounds, that is, compounds of the formula,

CuH4

and its salts, such as the alkali metal, nickel, iron and cobalt salts thereof. Since these two classes of compounds are distinct, they will be discussed separately.

SAFRANINE COMPOUNDS Our invention contemplates, as indicated, the use of safranine compounds of adequate solubility and of the indicated formula. The bonds connecting the CeHz groups to the nitrogen atoms are ortho to each other and may be single or double. It is not known with certainty which. Reference is made to Schultz, infra for accepted theory of structure.

The salts of such of these compounds as are basic, e. g. the chlorides, hydrochlorides, acetates and sulfates are to be preferred to such basic compounds themselves because of their greater solubility. It is essential that these compounds, a single one or a mixture of two or more thereof, be present in the solution to an extent to exert their brightening effect, preferably at least two milligrams per liter.

Some specific examples of compounds suitable for our purpose are as follows, being identified where possible by reference to Farbstofitabellen by Gustav Schultz, 7th Edition, Volume I (1931).

Table I 1. ms-Phenyl ditolazonium chloride, a compound of the formula:

H5O N\ CH: )Cfi :Ch HzN NH:

01 CIHB 3. ms-Phenyl diamino diphenylazonium ride, a compound of the formula:

chlo- CIHPNH:

While the quantity of these substances employed is not sharply critical, they are used in small amounts, that is, amounts on the order of 2 to 100 milligrams per liter of the bath, the

upper limit being determined by their embrittling 5 efiect and in some cases, their solubility.

ORTHO Bmvzorc SULFIMIDES The second class of materials, representative particular ones or mixtures of which are employed in combination with one or more substances of the first class of compounds above identified are ortho benzoic sulfimides, specifically saccharine (acid compound) and its salts, such as the alkali metal, nickel, iron and cobalt salts. The sodium salt (soluble saccharine) is the preferred material, being readily available and relatively cheap. These materials are capable of cooperating with the materials of the first class to produce nickel deposits having a high order of brightness accompanied by commercial ductility. These addition agents of the second class are used in quantity from 0.1 gram per liter to saturation, preferably from 0.2 to 5.0 grams per liter.

A conventional aqueous acid nickel bath in which the combined use of the two classes of addition agents will be found to give improved results, as above indicated, consists of NiS04.6H2O 2 120-450 grams per liter NiCl2.6H2O -75 grams per liter H3303 15 grams per liter to saturation Sodium lauryl sulfate 1 01.0 gram per liter Current density" Up to 60 amperes per sq. ft. pH 1.5-5.5 Temperaturenu. Room to 170 F.

1 Where this compound is referred to, the material sold under the tradoname 0t Duponol M. E. Dry is understood. It is sold as the technical compound. Other equivalent surface tension reducing agents may be used instead of Duponol. Preparations known as Tergitol 7 and Tergitol 0S, sold by Carbide & Carbon Chemicals Co. and said to be sodium secondary alcohol sulfates, may be used instead of Duponol. The quantities required are of the same order.

Some heptahydrate is usually present. Where nickel sulfate is used herein in specific examples, this mixture of hydrates is to be understood.

In the above table giving the composition of a conventional bath, sodium lauryl sulfate is added for the purpose of reducing the surface tension in order to prevent pitting of the plate. The sulfates of normal primary aliphatic alcohols, having from 8 to 18 carbon atoms, are a class of compounds preferred for use for this purpose.

The following specific examples will serve to illustrate the invention:

Current density "amp/sq. ft

Example II Nickel sulfate grams 240 Nickel chloride do 37.5 Boric acid do 37.5 ms-Phenyl diamino diphenylazonium chloride do 0.01 o-Benzoic sulfimide (sa'ccharin,

sodium salt) do 2.0 10 Sodium lauryl sulfate do 0.25 Water to make liter 1 pH 4.0 Temperature C Current density amp./sq ft.. 40' 15 This application is a division of our cO-pending application, Serial No. 323,380yfi1ed March to be 11, 1940, now Patent No. 2,291,590, which was a continuation-in-part of application, Serial No. 217,774, filed July 6, 1938, now Patent No. 2,238,861.

Having thus described our invention, what we claim is:

1. An electroplating bath comprising an aqueous, acid solution of a nickel electrolyte of the class consisting of nickel sulfate, nickel chloride and mixtures thereof, said bath having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents being selected from the class consisting of compounds of the formula,

RI!!! N R J R' coal-R where R, R, R' and R" are selected from the class consisting of hydrogen, methyl and' Oit v 5/ and alkali metal, nickel, iron and cobalt salts thereof, and mixtures of such compounds and being present in the bath to the extent of at least 0.1 gram per liter.

2. An electroplating bath in accordance with claim 1, wherein the first mentioned addition agent is a mixture of ms-phenyl ditolazonium chloride and ms-o-tolyl ditolazonium chloride.

3. An electroplating bath in accordance with claim 1, wherein the first mentioned addition agent includes ms-phenyl ditolazoium chloride.

4. An electroplating bath in accordance with claim 1, wherein the first mentioned addition agent includes ms-o-tolyl ditolazonium chloride.

5. An electroplating bath in accordance with claim 1, wherein the first mentioned addition agent includes 'rns-phenyl diamino diphenyl azonium chloride.

6. An electroplating bath comprising an aqueous, acid solution of a nickel electrolyte of the class consisting of nickel sulfate, nickel chloride and mixtures thereof, said bath having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents being a mixture of ms-phenyl ditolazonium chloride and ms-o-tolyl ditolazonium chloride, and the other of said addition agents being selected from the class of compounds consisting of the compound of the formula v and alkali metal, nickel, iron and cobalt salts thereof, and mixtures of such compounds, said first mentioned addition agent being present in solution in the bath to the extent of from 2 to 100 milligrams per liter, and said second mentioned addition agent being present in solution in the bath to the extent of from 0.1 gram per liter to saturation.

7. An electroplating bath comprising an aqueous, acid solution of a nickel electrolyte of the class consisting of nickel sulfate, nickel chloride and mixtures thereof, said bath having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents including ms-phenyl ditolazonium chloride, and the other of said addition agents being selected from the class of compounds consisting of the compound of the formula chloride and mixtures thereof, said bath having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents including ms-o-tolyl ditolazonium chloride, and the other of said addition agents being selected from the class of compounds consisting of the compound of the formula tho and alkali metal, nickel, iron and cobalt salts thereof, and mixtures of such compounds, said first mentioned addition agent being present in solution in the bath to the extent of from 2 to milligrams per liter, and said second mentioned addition agent being present in solution in the bath to the extent of from 0.1 gram per liter to saturation.

9. An electroplating bath comprising an aqueous, acid solution of a nickel electrolyte oi the class consisting of nickel sulfate, nickel chloride and mixtures thereof, said bath having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents including ms-phenyl diamino diphenyl azonium chloride, and the other of said addition agents being selected from the class of compounds consisting of the compound of the formula and alkali metal, nickel, iron and cobalt salts thereof, and mixtures of such compounds, said first mentioned addition agent being present in solution in the bath to the extent of from 2 to 100 milligrams per liter, and said second mentioned addition agent being present in solution in the bath to the extent of from 0.1 gram per liter to saturation.

RUDOLF LIND. WILLIAM J. HARSHAW. KENNETH E. LONG. 

